Title: Understanding Hospitals' Responses to Mandatory Shared Decision Making Summary In 2016 CMS began covering percutaneous left atrial appendage closure (LAAC), a medical procedure designed to prevent strokes. As a condition of coverage, CMS required patients to undergo a ?shared decision making interaction? with an independent, non-interventional physician. CMS is poised to enact similar requirements for other procedures. The CMS requirement raises a number of important questions, such as: Is there a value to having a shared decision making interaction with an independent physician?, What determines whether a physician is independent?, Can independent physicians gauge patients' preferences and social and medical history?, Does the interaction change treatment decisions?, and Can patients make informed decisions in medically complex contexts? We propose to survey hospitals that perform the LAAC procedure to determine how they are implementing the CMS requirement and its impact on patient decisions. We will collect data on the specialty and organizational affiliation of the independent physician, when the interaction takes place, the content of the interaction, the degree of standardization, use of decision aids, whether the content of the interaction is modified for patients with low health literacy, and the rate of decision reversal. Results will help policymakers understand hospitals' compliance with the requirement and its impact on treatment decisions. Results will help researchers, who need to understand how shared decision making is conducted in routine practice in order to design interventions to improve it.